1. Field of the Invention
The invention relates to a scanner comprising means for converting the contents of a film frame into a video signal, means for post-processing the video signal and means for monitoring the post-processing result.
2. Description of the Related Art
Scanners having the features mentioned are used, for example, for storing the contents of lantern slides on magnetic storage means. A similar possibility of use is to store the contents of frames of a cinematographic film on video magnetic tapes, i.e., to make a copy of the cinematographic film in the form of a video film.
This transformation of the picture information from a record carrier to another requires a steady check in order that the quality of the copy is as similar as possible to that of the original. For example, when copying a color film, the color components in the video signal must be retuned. Other parameters of the video signal such as, for example, resolution, setup interval, gamma, white balance, drive and contour enhancement should also be monitored and, if necessary, changed.
These parameter values are performed at different positions (checkpoints) of the above-mentioned device for post-processing the video signal and applied, via a measuring crossbar, to a display apparatus such as, for example, an oscilloscope or a monitor.
An important parameter is the drive of the converter elements and their preamplifiers, i.e., those means with which a frame is converted into a corresponding amplified video signal. These means are, for example, opto-electronic converters such as solid-state sensors (CCDs) or pick-up tubes. Other means for this purpose are photomultipliers which convert a light beam modulated by the picture and generated by the electron beam of a flying spot tube into the video signal.
To optimize the drive of these elements, the intensity of the light in the first of the above-mentioned cases, or the intensity of the electron beam in the second case, should be increased or decreased. To control the drive, an input of the crossbar is connected to a checkpoint directly behind the converter. Since it is often necessary to change the drive of the opto-electronic converter simultaneously with the change of the video signal parameters, the crossbar should consequently be switched continually back and forth. In digital systems, a complicated D/A conversion dependent on the data format must be performed per checkpoint, because the picture is shown on the oscilloscope or the monitor in an analog form. This involves quite a considerable temporal and circuit-technical cost and a large number of components, which is normally not justifiable.